The president said there "were a lot of close elections" and "every single one of them went Democrat."

"There's something going on," he said, and warned Republicans that they need to "be a little bit more paranoid than you are, OK?"

"We have to be a little bit careful, because I don't like the way the votes are being tallied. I don't like it and you don't like either, you just don't want to say it because you're afraid of the press," he said.

In the days after the midterm elections, Trump fanned election fraud fears as votes were counted in close races. He tweeted about "Election Fraud" and "Election Theft" in Florida as that state's U.S. Senate and gubernatorial races drew closer in late vote counting. Eventually, the Republicans were confirmed as the winner in both races.

The president went further with his concerns and called for a new election in the Senate race in Arizona, where Democrat Kyrsten Sinema overcame Republican Martha McSally in late vote counting. McSally had held a lead on election night.

But experts pointed out that extended vote counting in Arizona was nothing unusual. In an article for The Washington Post, Charles Stewart III, the director of the MIT Election Data and Science Lab, said that since 2000, late vote counting has generally favored Democrats across the nation in what political scientists have referred to as the "blue shift."

He said there are two primary causes for that trend. First, more minority and young voters with contested registrations have been casting provisional ballots – both groups that tend to favor Democrats. Second, Democrats are more likely to vote by mail.

One 2018 election result was thrown out over fraud concerns. In North Carolina's 9th Congressional District, Republican Mark Harris' campaign was accused of improperly collecting absentee ballots. Trump did not mention that race in his speech Tuesday.

After taking office, Trump established the Presidential Advisory Commission on Election Integrity to investigate his suspicion that millions of people voted illegally in the 2016 election. But the commission was disbanded after less than eight months without uncovering any evidence of voter fraud.

Despite his concerns about electoral corruption, Trump said he is "totally confident" that the Republicans will retake the House in 2020.